Vehicles pinball as fog and smoke create a deadly mix. A stretch of interstate remains closed.

WINTER HAVEN -- Jacque Provau was driving to see a doctor in Orlando early Wednesday morning when her Mazda van entered a thick fog. Traffic ahead on Interstate 4 abruptly stopped.

"All you saw was brake lights and heard people hitting people," said Provau, 59, of St. Petersburg. "I heard people yelling. I heard them screaming. It was horrible."

Then she saw two Beall's department store trucks ahead of her. They were burning.

In the fog, a chain-reaction of crashes among 70 vehicles killed at least four people, sent 38 more to three hospitals and led officials to close indefinitely a 14-mile stretch of Central Florida's main east-west highway.

"Don't plan any road trips on the interstate in the near future," said Polk County Sheriff Grady Judd.

State investigators are trying to determine how a controlled burn on a state wildlife management area got out of control, and what role it played in the tragedy.

About 10 a.m. Tuesday, the staff of the Hilochee Wildlife Management Area started the burn on 10 acres along I-4, part of an effort to clear land for better wildlife habitat.

Somehow, it turned into a 400-acre wildfire.

Two years of drought have left most of Florida extremely dry. A Division of Forestry map of the state's driest areas shows I-4 as a deep red, meaning it is a high risk for a wildfire.

Firefighters were called in to battle the blaze about 11 a.m. Tuesday but were unable to bring it under control. By Tuesday evening, signs were posted along heavily traveled I-4, warning the 75,000 motorists who use that stretch daily about the fog and smoke.

By early Wednesday, the scene had turned to chaos.

Hurt deputy a rescuer

Charles Edwards, 49, of Brandon was eastbound on I-4 Wednesday morning when he saw what seemed like "a big wall of smoke."

"I jumped out of my vehicle. It's just unreal."

Before dawn, smoke from the fire mixed with a patch of dense, ground-hugging fog. Visibility on the road dropped to zero, a condition Sheriff Judd described as "total darkness."

"When I tell you you could not see your hand in front of your face, that is not an exaggeration," Judd said.

The smoke is what caused the fog to thicken, said Tom Dougherty, a forecaster with the National Weather Service.

"It wasn't foggy near the Tampa Bay area at all. It was a very small localized area in the interior, in that part of Polk County," Dougherty said. "Apparently the trigger mechanism behind it was the smoke from the burns they had near the roadway."

Particles in the smoke gave water vapor in the fog something to cling to, making it thicker, he said.

"When the fog hits that smoke, there's a multiplying effect," Dougherty said. "It got very dense and very dangerous."

The Highway Patrol logged the first I-4 crash at 5 a.m., and noted that because of the mingled fog and smoke there was "zero visibility" between mile markers 43 and 49.

It was so thick that aerial photos made it look like a blizzard had hit Florida and dumped 6 feet of snow.

In the darkness, a typical rush hour turned into a deadly demolition derby.

Linda Turner was driving along in her silver two-door Toyota Yaris when she heard the screeching of metal. Around her, dozens of cars -- including a Polk County sheriff's cruiser -- began slamming into each other.

Through the fog, in fleeting glimpses, Turner saw overturned tanker trucks on fire, a badly damaged gold Toyota Camry rear-ended with its trunk in the front seat, and a mangled minivan that eventually was carted off the scene atop a flatbed tow truck.

Sheriff Judd said one of his deputies, Carlton Turner, was among the first involved in what would become a chain of wrecks.

"He got banged around," Judd said. "As he tried to get out of his car, other cars banged into him."

The deputy pulled his car about 50 feet off the highway, Judd said. Then, despite his own injuries, he climbed out to try to take charge of the crash scene. He told motorists who climbed out of their vehicles to return to their cars before they got run over.

When he saw injured people he tried to pull them out. In some cases, he did not succeed.

Judd said the deputy told him, "I watched a man burn to death today. I heard others screaming, hollering and crying. I can't begin to explain to you how difficult this scene was. I can't explain to you the trauma that occurred."

Authorities had not released the identities of the four dead Wednesday evening.

But the Orlando Sentinel reported that Disney officials confirmed that one of its employees died in the accident. Darren Scott Snyder worked in engineering services on the maintenance team at the Animal Kingdom.

At least six trucks and five cars burned up. Several trucks burned down to the frame.

And in the aftermath, the squads of rescuers combing the wreckage for victims discovered that even flashlights were useless in the souplike fog.

Only screams cut fog

Carpenter Paulino Duenas and his friend Eduardo Donoso were headed from St. Petersburg to St. Cloud to look for work when their Taurus struck the rear of a semitrailer truck.

Another car then slammed into the Taurus.

That was about 5:30 a.m. With his knee, hips and ankle injured, Duenas, 40, waited for help.

Rescue crews didn't reach him for more than two hours, finally arriving about 8 a.m., he said. All the two men could do was bear witness to the horrific scene around them.

"Help my wife," they heard someone shout.

"Get me out of here," someone else pleaded.

Because of the fog, deputies and rescue crews could not drive through the crash scene safely. They also could not see who was in need of assistance.

Instead, they had to walk along the highway, listening for victims' cries, then try to locate them. The last crash victim, trapped in an overturned truck, wasn't rescued until after 11 a.m.

Helicopter pilots could not land at the scene. More than a dozen crash victims were loaded onto a school bus to be taken to a hospital.

The same nightmarish mix of fog and smoke could recur this morning, forecasters warn.

"The conditions will be similar," said Dougherty, of the weather service. "We're still forecasting fog after midnight, with a light east wind. The best case scenario is, the wind will become a little bit stronger. If we get an east wind at 5 mph, that would help out a lot. If they go dead calm again, same as they did (Wednesday) morning, you certainly could see the same thing happen."

The wild card is the smoke.

"We have no way of knowing how significant the fire will be," Dougherty said.

By Wednesday afternoon, the fire was contained, but far from out. Jim Brenner of the state Division of Forestry said it's possible the blaze could turn into a "muck fire" -- meaning organic soil beneath the surface of the ground begins to smolder. Putting out a muck fire is a laborious process that requires turning the soil over and soaking it down.

The other problem with working a fire in muck is that the firefighters' tractors can easily get bogged down. It happened twice Tuesday. One of those tractors was saved, but the other caught fire and burned.

To complicate matters, about 500 acres caught fire in this region in 2001, in a blaze known as the "Stagecoach Fire." That left downed cypress trees and other debris that made it difficult for firefighters to maneuver equipment around it in battling the Hilochee blaze.

State officials were not saying much Wednesday about the Hilochee controlled burn, the wildfire that followed and what role they may have played in the I-4 wrecks.

Department of Agriculture investigators said they are still looking into what caused the wildfire and whether it led to the crashes.

Times staff writers Curtis Krueger and Alex Zayas contributed to this story.